Effects of Milk Replacer-Based Lactobacillus on Growth and Gut Development of Yaks’ Calves: a Gut Microbiome and Metabolic Study

ABSTRACT The gut microbiota and its metabolic activities are crucial for maintaining host homoeostasis and health, of which the role of probiotics has indeed been emphasized. The current study delves into the performance of probiotics as a beneficial managemental strategy, which further highlights their impact on growth performance, serologic investigation, gut microbiota, and metabolic profiling in yaks’ calves. A field experiment was employed consisting of 2 by 3 factorial controls, including two development stages, namely, 21 and 42 days (about one and a half month), with three different feeding treatments. Results showed a positive impact of probiotic supplements on growth performance by approximately 3.16 kg (P < 0.01) compared with the blank control. Moreover, they had the potential to improve serum antioxidants and biochemical properties. We found that microorganisms that threaten health were enriched in the gut of the blank control with the depletion of beneficial bacteria, although all yaks were healthy. Additionally, the gut was colonized by a microbial succession that assembled into a more mature microbiome, driven by the probiotics strategy. The gut metabolic profiling was also changed significantly after the probiotic strategy, i.e., the concentrations of metabolites and the metabolic pattern, including enrichments in protein digestion and absorption, vitamin digestion and absorption, and biosynthesis of secondary metabolites. In summary, probiotics promoted gut microbiota/metabolites, developing precise interventions and achieving physiological benefits based on intestinal microecology. Hence, it is important to understand probiotic dietary changes to the gut microbiome, metabolome, and the host phenotype. IMPORTANCE The host microbiome is a composite of the trillion microorganisms colonizing host bodies. It can be impacted by various factors, including diet, environmental conditions, and physical activities. The yaks’ calves have a pre-existing imbalance in the intestinal microbiota with an inadequate feeding strategy, resulting in poor growth performance, diarrhea, and other intestinal diseases. Hence, targeting gut microbiota might provide a new effective feeding strategy for enhancing performance and maintaining a healthy intestinal environment. Based on the current findings, milk replacer-based Lactobacillus feeding may improve growth performance and health in yaks’ calves.

I have received the reviews of your manuscript entitled "Effects of milk replacer-based Lactobacillus on growth and gut development of yak's calves; A gut microbiome and metabolic base study". The reviewers were generally positive about the outlook and theme of the work but found that it was not possible to properly evaluate the science because the English in the manuscript needed to be improved. Therefore, even though Spectrum does not normally consider resubmissions of rejected manuscripts, we are willing in this instance to make an exception. However, I would like to note that I will be looking for a robust revision that makes the results of the manuscript able to be clearly interpreted. To improve the English you may wish to work with a colleague or to use one of the services recommended here https://journals.asm.org/content/language-editing-services . Also, please note that the revision you submit will be subjected to another round of review and I will be looking for you to address Reviewer 1's comments in your revision as well. Finally, if you choose to pursue this option, please write to the editorial spectrum@asmusa.org BEFORE submitting your revised paper.
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Reviewer comments: Reviewer #1 (Comments for the Author): Overall, the manuscript is interesting, the methods are approproate, and the results are well presented. The manuscript could use an additional spelling and grammar check, and I included some minor corrections here: line 14: correct to "highlights" line 26" remove the hyphen line 29: correct to "probiotics dietary supplements changes the" line 33: correct to "collaterally" line 39, 454, 458, 460, Fig 1 legend: correct to "yak calves" line 42: italicize the species' name line 60: correct to "probiotics is suspected to be a vital feeding strategy as" line 62: while this sentence is true, since this paper focuses on cattle it would be more informative to include a reference on improving calf health here instead of one on human infants. lines 68-76: was this research on any species of Lactobacillus? I think many of the benefits are species or strain specific, so the authors should be more specific. For example, "...therapy of certain Lactobacillus species modulated..." line 85: "establishment of microbiota" line 103: "yak calves' microbiome" line 108: I would change 'microbiome' to 'bacterial community' here and elsewhere in the manuscript because 16S only gives a fraction of the microbiome and is misleading to use. line 136: correct to "diversity" lines 158 -159: italicize the genera names here lines 185: I am not sure what the authors means by "kept tendancy", please revise line 193, 248, 250, 253, 323: revise to "yak calves" line 404: "vitamins" Figures: the text in the figures was too small to read since there were so many panels. I recommend moving some of these to supplementary, or splitting figures into two as needed to make the panels and text larger.
Reviewer #2 (Comments for the Author): The manuscript submitted by Li et al. demonstrates a milk replacer-based lactobacillus in the yak's calves could increase the body weight. It may be interesting to those who are working in this field. However, this manuscript is with too many typos and grammar problems. In many areas, I don't what the authors try to say. I suggest that the author ask a native English speaker to edit your manuscript.

Subject: Response to Reviewer's Comments
Kindly, refer to your email May 4, 2022, regarding our submitted manuscript ID (Spectrum01155-22) entitled "Effects of milk replacer-based Lactobacillus on growth and gut development of yak's calves; A gut microbiome and metabolic base study". Based on reviewer comments, we, the authors, have carefully incorporated suggestion to the manuscript, and we hope that the revised-manuscript now will meet the standards for publication in your good journal.
We are looking forward to hearing from you soon. Your manuscript has been accepted, and I am forwarding it to the ASM Journals Department for publication. You will be notified when your proofs are ready to be viewed.
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